bluez5: backend-native: don't use libbluetooth hci commands

BlueZ 6 is planning to make most of libbluetooth private.  In
particular, the direct hci access is planned to be removed.  This is
currently used for determining adapter msbc support.

Instead of using libbluetooth API, try to determine msbc support by
a connect() attempt, which the kernel should reject when not supported.